[455bird]

Picked up a 1969 Firebird 400 convertible project that appears to have a Blazer S10 rear disc brake conversion, with stock 11" discs (D52 calipers) up front. It has a hydroboost system, with the pedal rod in the upper (manual) brake hole and a 1" aluminum master cylinder from a 1997 Buick fullsize (4 wheel disc car) along with an adjustable proportioning valve on the rear brake line. There is no factory proportioning valve. The problem is that the proportioning valve is backed all the way off and the front brakes still lock way before the rears. In fact the rears never really lock. I don't see any residual valves in the master cylinder or anywhere in the rear brake line. The car stops fine under normal driving, but when driven aggressively, it just doesn't feel like it's getting the most out of the rear discs. Any ideas of what is wrong? Would more aggressive brake pads like Hawk sells help with the rear grip?